KR100810998B1 - Prismatic film and manufacturing method thereof - Google Patents

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prism film used in a back-light unit of a liquid crystal display and a method of manufacturing the same, wherein the prism is formed on one surface of the base film using a base film and a plastic material for ultraviolet polymerization. A prism film comprising a structure layer, and having a chemical resistance index (L) of 85% or more with respect to an organic solvent calculated by the following formula, and continuously produced, including primary and secondary ultraviolet curing processes In the manufacturing method of, The process at the time of secondary hardening provides the manufacturing method of the prism film characterized by the air atmosphere whose oxygen concentration is 5% or less.

Chemical Resistance Index (L) = 100-{(L ₀ -L ₁ ) / L ₀ × 100}

(L ₀ : vertical brightness of backlight unit with prism film not immersed in organic solvent, L ₁ : vertical brightness of backlight unit with prism film after immersion in organic solvent for 30 minutes and dried at room temperature for 10 minutes , The luminance is measured as described in the text.)

According to the above configuration, the present invention can prevent a decrease in luminance due to a cleaning process and can remove a polymerization inhibition caused by oxygen to improve chemical resistance to an organic solvent.

Liquid Crystal Display, Prism Film, Luminance, Chemical Resistance, UV Curing, Photoinitiator

Description

Prism film and its manufacturing method {PRISMATIC FILM AND MANUFACTURING METHOD THEREOF}

1 is a schematic diagram showing a continuous manufacturing process of a prism film;

Figure 2 is a photograph taken with an electron microscope of the surface state after immersing the prism film of an embodiment of the present invention in an organic solvent for 30 minutes.

Figure 3 is a photograph taken with an electron microscope of the surface state after immersing the prism film of the comparative example of the present invention in an organic solvent for 30 minutes.

[Description of main part of drawing]

10 base film 20 plastic material for ultraviolet polymerization

30: prism film 40: plastic material injection device for ultraviolet polymerization

50: cylindrical mold 60: adhesive roll

70: primary ultraviolet curing device 80: secondary ultraviolet curing device

90 gas injection device

The present invention relates to a prism film used in a back-light unit of a liquid crystal display.

In order to increase the front luminance of the backlight unit, the prism film is usually disposed on the light diffusing plate or the upper part of the light diffusing film and uniformly diffuses and emits light in various directions to the front using the function of total reflection and refraction of the prism structure. It is a film which improves a brightness | luminance as much as possible. The brightness enhancement function is a phenomenon occurring at the interface of the prism structure. In order to function properly, the interface of the prism structure must be uniform, and in order to make the interface uniform, the surface roughness of the prism structure must be kept smooth. . That is, the surface uniformity of the prism structure of the prism film becomes a very important factor with respect to the brightness enhancement function.

In general, the prism film has a large amount of foreign matters attached to the surface due to its surface structure. Therefore, before the prism film is attached to the backlight unit, it is possible to manage organic matters such as methanol, ethanol, isopropyl alcohol, methyl ethyl ketone and the like. The solvent is used for cleaning. At this time, the conventional prism film has a problem that the brightness after the cleaning process is lower than the brightness before the cleaning process.

Initial prism film is a method of cooling a mold by heating a mold having a prism structure shape to a certain temperature, placing a polymerized plastic material thereon, applying pressure to the mold, and then cooling the mold. The prism film thus prepared did not show a significant decrease in luminance after the above-described cleaning process.

However, such a manufacturing method has a disadvantage of being unsuitable for mass production due to the unit process, which is not widely used at present.

Accordingly, in order to mass-produce the prism film in a continuous process, as shown in FIG. 1, the plastic material 20 for ultraviolet polymerization is coated on the cylindrical mold 50 in which the prism structure is carved, and the base film 10 is In the state in which the coating 20 is wrapped, ultraviolet light is passed through the base film 10 from the primary ultraviolet curing device 70 to inject the coated plastic material 20 for ultraviolet polymerization, thereby injecting the plastic material for ultraviolet polymerization. The prism film 30 is produced in such a manner that 20 polymerizes in the form of a prism structure inscribed in the cylindrical mold 50.

In addition, since the final prism film maintains the cylindrical shape when the ultraviolet-polymerizing plastic material 20 completes the polymerization only by the primary curing in the state in close contact with the cylindrical mold 50 as described above, In the state where the ultraviolet-polymerizing plastic material 20 is in close contact with the cylindrical mold 50, ultraviolet ray energy may be polymerized to the extent that the ultraviolet-polymerizing plastic material 20 can be released from the cylindrical mold 50. It is preferable to finish hardening by irradiating and adjusting and irradiating an ultraviolet-ray from the secondary ultraviolet curing apparatus 80 after demolding from the said cylindrical metal mold | die 20.

However, after the mold release from the cylindrical mold 50, the secondary curing from the secondary ultraviolet curing device 20, unlike the primary curing from the primary ultraviolet curing device 70, the primary cured ultraviolet polymerization Secondary curing takes place when the surface of the plastic material is exposed to air. At this time, oxygen in the air acts as a radical polymerization inhibitor, thereby slowing down the polymerization rate and causing low molecular polymerization. Cause.

Therefore, in the continuous process for mass production of the prism film, the polymerization inhibition phenomenon occurs due to the influence of oxygen during the second curing, and in particular, the polymerization state of the surface becomes poor, and thus, when the cleaning process using the volatile organic solvent is processed, FIG. 3. As in the photo of the surface erosion is made, there is a problem in maximizing the brightness degradation phenomenon of the prism film eventually.

An object of this invention is to provide the prism film which prevented the brightness fall phenomenon by the cleaning process mentioned above.

The present invention provides a prism film including a base film and a prism structure layer formed on one surface of the base film as a plastic material for ultraviolet polymerization, and having a chemical resistance index (L) of 85% or more for an organic solvent calculated by the following equation. .
Chemical Resistance Index (L) = 100-{(L ₀ -L ₁ ) / L ₀ × 100}

(L ₀ : vertical brightness of backlight unit with prism film not immersed in organic solvent, L ₁ : vertical brightness of backlight unit with prism film after immersion in organic solvent for 30 minutes and dried at room temperature for 10 minutes )

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The plastic material for ultraviolet polymerization included in the prism structure layer may include a monomer or oligomer for ultraviolet polymerization; The photocuring agent includes a primary curing photoinitiator sensitive to ultraviolet rays in the wavelength range of 310 nm or less and a secondary curing photoinitiator sensitive to ultraviolet rays in the wavelength range of 310 nm or more.

The primary curing photoinitiator is characterized in that the phosphine oxide-based photoinitiator.

The secondary curing photoinitiator is a phenylglyoxylate-based or hydroxyketone-based photoinitiator It is characterized by one or more selected from.

In another aspect, the present invention is a primary ultraviolet curing process of coating a plastic material for ultraviolet polymerization on the cylindrical mold in which the prism structure is stamped and wrapping the plastic material for ultraviolet polymerization with a base film and then scanning ultraviolet rays; And a secondary ultraviolet curing step of releasing the ultraviolet-polymerizing plastic material from the cylindrical mold and irradiating ultraviolet rays, wherein the secondary ultraviolet curing step is an air atmosphere during secondary curing. It provides a method for producing a prism film, characterized in that the oxygen concentration is 5% or less.

The secondary ultraviolet curing process is characterized in that the oxygen atmosphere is adjusted by injecting one kind of gas selected from nitrogen gas, argon gas, helium gas, and neon gas as the air atmosphere during the secondary curing.

Hereinafter, the present invention will be described in more detail.

The prism film of the present invention has excellent chemical resistance against volatile organic solvents (selected among methanol, ethanol, isoprephyl alcohol, and methyl ethyl ketone) which are generally used in the cleaning process, and the chemical resistance index of each of the volatile organic solvents is measured from a relationship between the initial luminance (L ₀₎ and the luminance (L ₁₎ after immersion for 30 minutes each of the volatile organic solvents of the present inventors prism film, characterized in that 85% or more. If the chemical resistance index is 85% or more, the performance of the prism film may be sufficiently exhibited in the backlight unit even after the cleaning process. If the chemical resistance index is less than 85%, the luminance performance of the prism film may be deteriorated to be used in the backlight unit. The performance is poor.

The base film of the prism film of this invention can use 1 type of a polyethylene terephthalate film, a polycarbonate film, a polypropylene film, a polyethylene film, a polystyrene film, or a polyepoxy film, Among these, a polyethylene terephthalate film is preferable.

The base film has a thickness of 10 to 1000 µm, more preferably 25 to 500 µm. If the thickness of the base film is less than 10㎛, there is a problem that the mechanical strength and thermal stability is weak, if the thickness of more than 1000㎛ may reduce the flexibility of the film, loss of light transmittance may occur.

The plastic material for ultraviolet polymerization forming the prism layer of the prism film of the present invention comprises a mixture of a monomer or oligomer for ultraviolet polymerization and a photoinitiator, and the monomer or oligomer preferably has a refractive index of 1.55 or more, and examples thereof include a polyaromatic acrylic monomer. Or a monomer having a high refractive index such as a brominated aromatic acrylic monomer or a sulfur-containing aromatic acrylic monomer, or an oligomer having such a monomer as a main chain.

The photoinitiator is preferably included 0.1 to 5.0% by weight of the total composition, if less than 0.1% by weight does not achieve sufficient photocuring occurs blocking phenomenon, if more than 5% by weight yellowing by the remaining photoinitiator after curing Precipitation or precipitation of remaining photoinitiators occurs.

In order to improve chemical resistance with respect to the above-mentioned organic solvent as a prism film of this invention, it is preferable to use 2 or more types of said photoinitiators.

When the prism film is manufactured in a continuous manufacturing process as shown in FIG. 1, when curing the plastic material for ultraviolet polymerization, the primary cured film and the secondary cured resin are cured. Since the ultraviolet light from the device 70 passes through the base film 10 and reaches the plastic material 20 for ultraviolet polymerization, the photoinitiator can be sensitive to ultraviolet light in a wavelength band not absorbed by the base film 10. You need to choose.

Since the base film mainly absorbs light in the wavelength range of 310 nm or less, the photoinitiator of the present invention is a photoinitiator (hereinafter referred to as a primary curing photoinitiator) at an optical wavelength band of 310 nm or more, and a photoinitiator sensitive at an optical wavelength band of 310 nm or less By mixing (hereinafter referred to as a secondary curing photoinitiator), the photocurability of the plastic material for ultraviolet polymerization used in the present invention can be further improved to improve chemical resistance to an organic solvent.

It is preferable that the primary curing photoinitiator is a phosphine oxide-based photoinitiator, and the secondary curing photoinitiator is a phenylglyoxylate-based photoinitiator or a hydroxyketone-based photoinitiator.

On the other hand, the present invention is a primary ultraviolet curing process of coating the ultraviolet light polymerization plastic material on the cylindrical mold in which the prism structure is stamped and wrapped with the base material film, the ultraviolet light and then scanning the ultraviolet light; And a secondary ultraviolet curing step of releasing the ultraviolet-polymerizing plastic material from the cylindrical mold and irradiating ultraviolet rays, wherein the secondary ultraviolet curing step is an air atmosphere during secondary curing. It provides a method for producing a prism film, characterized in that the oxygen concentration is 5% or less.

Therefore, as described in the related art, chemical resistance to the organic solvent may be improved by removing the inhibition of polymerization by oxygen during secondary curing, which was a problem when the prism film is manufactured in a continuous manufacturing process.

That is, in the secondary ultraviolet curing step, it is preferable to form and cure the air atmosphere during secondary curing in an oxygen low concentration atmosphere of about 5% or less, and at this time, the oxygen concentration is more preferably about 2% or less.

At this time, in order to create an oxygen low concentration atmosphere, it is preferable to inject one gas selected from nitrogen gas, argon gas, helium gas, and neon gas through the gas injection device 90 at the time of secondary curing.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the scope of the present invention is not limited to the following Examples.

<Example 1>

Epoxyacrylate (CN120, Satomer) 39% by weight, ethoxylated bisphenol A diacrylate (SR-349, Satomer) 39% by weight, 1,6 hexanedioldiacrylate (SR-238, Satomer) 7.5 wt%, Tris (2-hydroxyethyl) isocyanurate triacrylate (SR-368, Satomer) 11.5 wt%, 2,4,6-trimethylbenzoyldiphenyl phosphine oxide (DAROCUR TPO, CIBA) 3 wt% is mixed to prepare a plastic material for ultraviolet polymerization.

A polyethylene terephthalate film (FHZZ, KOLON) having a thickness of 125 μm was put into a cylindrical mold together with the plastic material for ultraviolet polymerization and irradiated with ultraviolet rays of 200 mJ / m 2 (Fusion, 600 W / inch, D bulb) for primary curing. Let's do it. The first cured prism film was cured by irradiating ultraviolet light at 800 mJ / m 2 (Fusion, 600 W / inch, D bulb) under nitrogen gas filling (oxygen concentration of 1%) to prepare a prism film.

<Example 2>

40% by weight brominated epoxydiacrylate (RDX 51027, UCB), 30% by weight 6-functional urethane acrylate (EB220, UCB), 27% by weight benzine methacrylate (airborne), 2,4,6- as photoinitiator 3% by weight of trimethylbenzoyldiphenyl phosphine oxide (DAROCUR TPO, CIBA) is mixed to prepare a plastic material for ultraviolet polymerization.

Thereafter, the prism film was manufactured in the same manner as in Example 1.

<Example 3>

Epoxyacrylate (CN120, Satomer) 39% by weight, ethoxylated bisphenol A diacrylate (SR-349, Satomer) 39% by weight, 1,6 hexanedioldiacrylate (SR-238, Satomer) 7.5 weight%, tris (2-hydroxyethyl) isocyanurate triacrylate (SR-368, Satomer), 11.5 weight%, 2,4,6-trimethylbenzoyldiphenyl phosphine oxide as a primary curing photoinitiator ( DAROCUR TPO, CIBA) 1.5% by weight and 1.5% by weight of the phenoglyoxylate (DAROCUR MBF, CIBA) as a secondary curing photoinitiator to prepare a plastic material for ultraviolet polymerization.

A polyethylene terephthalate film (FHZZ, KOLON) having a thickness of 125 μm was put into a cylindrical mold together with the plastic material for ultraviolet polymerization and irradiated with ultraviolet rays of 200 mJ / m 2 (Fusion, 600 W / inch, D bulb) for primary curing. Let's do it. The first cured prism film was irradiated with ultraviolet rays of 800 mJ / m 2 (Fusion, 600 W / inch, D bulb) and then cured to prepare a prism film.

<Example 4>

40% by weight brominated epoxydiacrylate (RDX 51027, UCB), 30% by weight 6-functional urethane acrylate (EB220, UCB), 27% by weight benzine methacrylate (conjugated), 2,4 as primary curing photoinitiator A plastic material for ultraviolet polymerization was prepared by mixing 1.5 wt% of, 6-trimethylbenzoyldiphenyl phosphine oxide (DAROCUR TPO, CIBA) and 1.5 wt% of a pheniglyoxylate (DAROCUR MBF, CIBA) as a secondary curing photoinitiator.

Thereafter, the prism film was manufactured in the same manner as in Example 3.

Example 5

Prepared by the same materials and methods as in Example 3, but the secondary curing in the state of nitrogen gas filled (oxygen concentration 1%) during secondary curing to prepare a prism film.

<Example 6>

Prepared by the same materials and methods as in Example 4, but the secondary curing in the state of nitrogen gas filled (oxygen concentration 1%) during secondary curing to prepare a prism film.

Comparative Example 1

A prism film was prepared by preparing the same material and method as in Example 1, but performing secondary curing without adding nitrogen gas during secondary curing.

Comparative Example 2

A prism film was prepared by preparing the same material and method as in Example 2, but performing secondary curing without adding nitrogen gas during secondary curing.

How to evaluate chemical resistance index

① The four prism films of Examples 1 to 6 and Comparative Examples 1 and 2 were alternately mounted in the same 17-inch backlight unit (Model: LM170E01, Heesung Electronics, Korea) and the luminance meter (Model: BM-7, Japan TOPCON) The average value L ₀ is obtained by measuring the luminance at any 13 points using.

② Four samples of each of the prism films of the above examples and comparative examples were immersed in methanol, ethanol, isopropyl alcohol and methyl ethyl ketone of general grade (Samjeon Pure Chemical Industries, Ltd.) for 30 minutes, and then taken out and dried for 10 minutes.

(3) Measure the luminance (L ₁ ) of the sample immersed in the organic solvent and dried by the luminance measuring method of ①.

④ Chemical resistance index (L) = 100-{(L ₀ -L ₁ ) / L ₀ × 100}
(L ₀ : vertical brightness of backlight unit with prism film not immersed in organic solvent, L ₁ : vertical brightness of backlight unit with prism film after immersion in organic solvent for 30 minutes and dried at room temperature for 10 minutes )

The brightness in the backlight unit of the prism films prepared according to Examples 1, 2 and Comparative Example 1 was measured, respectively, and immersed for 30 minutes using methanol, ethanol, isopropyl alcohol, and methyl ethyl ketone as organic solvents. In the case of, the luminance in the backlight unit was measured, and the chemical resistance index was calculated in the above formula. The results are shown in Table 1 below.

division Used organic solvent Luminance before immersion L ₀ (Cd / ㎡) Luminance L ₁ (Cd / ㎡) after immersion in organic solvent for 30 minutes Chemical resistance index (%) Example 1 Methanol 3500 3255 93 ethanol 3501 3466 99 Isopropyl Alcohol 3500 3395 97 Methyl ethyl ketone 3502 3327 95 Example 2 Methanol 3754 3416 91 ethanol 3755 3604 96 Isopropyl Alcohol 3754 3491 93 Methyl ethyl ketone 3757 3569 95 Example 3 Methanol 3503 3082 88 ethanol 3501 3220 92 Isopropyl Alcohol 3502 3256 93 Methyl ethyl ketone 3501 3186 91 Example 4 Methanol 3755 3417 91 ethanol 3760 3572 95 Isopropyl Alcohol 3753 3565 95 Methyl ethyl ketone 3756 3568 95 Example 5 Methanol 3500 3290 94 ethanol 3501 3326 95 Isopropyl Alcohol 3502 3397 97 Methyl ethyl ketone 3501 3430 98 Example 6 Methanol 3753 3490 93 ethanol 3751 3451 92 Isopropyl Alcohol 3750 3638 97 Methyl ethyl ketone 3750 3375 90 Comparative Example 1 Methanol 3495 2796 80 ethanol 3501 2941 84 Isopropyl Alcohol 3500 2940 84 Methyl ethyl ketone 3498 2903 83 Comparative Example 2 Methanol 3753 2815 75 ethanol 3752 3001 80 Isopropyl Alcohol 3753 3115 83 Methyl ethyl ketone 3751 3151 84

The prism film prepared according to Example 1 was wiped off using methanol, and the prism film prepared according to Comparative Example 1 was wiped off using methanol for 1000 times. Photographs were taken and observed at magnification, and the results are shown in FIGS. 2 and 3, respectively.

In the prism film of FIG. 2, the surface of the prism structure is not changed by methanol, but the prism film of FIG. 3 can be seen that the surface of the prism structure is severely damaged by methanol. That is, the prism film of FIG. 3 is vulnerable to an organic solvent, and when the cleaning process is performed using an organic solvent to remove foreign substances on the surface of the prism film, the prism film affects the uniformity of the surface of the prism film, and thus, the luminance deteriorates. have.

As described above, in Examples 1 to 6 based on the present invention, it can be seen that the chemical resistance index is 90% or more. Therefore, the prism film of the present invention has excellent chemical resistance, so that the phenomenon of deterioration in brightness due to the cleaning process It can be seen that it does not occur, the chemical resistance index of Comparative Examples 1 and 2 is less than 85%, it can be seen that the phenomenon of brightness degradation due to the cleaning process is very severe.

As described above, the present invention provides a prism film having a chemical resistance index of 85% or more with respect to an organic solvent, thereby preventing a decrease in luminance due to a cleaning process.

Claims (6)

In the prismatic film comprising a (correction) base film and a prism structure layer formed on one surface of the base film with a plastic material for ultraviolet polymerization, The prism film is a prism film , characterized in that the chemical resistance index (L) of 85% or more with respect to the organic solvent calculated by the following equation. Chemical Resistance Index (L) = 100-{(L ₀ -L ₁ ) / L ₀ × 100} (L ₀ : vertical luminance of a backlight unit with a prism film not immersed in an organic solvent, L ₁ : vertical ignition of a backlight unit with a prism film after immersion in an organic solvent for 30 minutes and dried at room temperature for 10 minutes. In addition, the brightness is measured as described in the detailed description of the invention . ) (Correction) The method according to claim 1, Plastic material for ultraviolet polymerization included in the prism structure layer, A monomer or oligomer for ultraviolet polymerization; The photocuring agent includes a primary curing photoinitiator sensitive to ultraviolet rays in the wavelength range of 310nm or less, and a secondary curing photoinitiator sensitive to ultraviolet rays in the wavelength range of 310nm or more , wherein the primary curing photoinitiator is a phosphine oxide-based photoinitiator, Secondary curing photoinitiators are phenylglyoxylate- or hydroxyketone-based photoinitiators It is 1 or more types chosen from the prism film characterized by the above-mentioned . (delete) (delete) A primary ultraviolet curing process of coating a plastic material for ultraviolet polymerization on a cylindrical mold having a prism structure stamped therein, wrapping the plastic material for ultraviolet polymerization with a base film, and then scanning ultraviolet light; And In the method of manufacturing a prism film, including a secondary ultraviolet curing step of releasing ultraviolet light after releasing the plastic material for ultraviolet polymerization from the cylindrical mold, The secondary ultraviolet curing step is a method for producing a prism film, characterized in that the air atmosphere at the time of secondary curing is less than 5% oxygen concentration. The method of claim 5, wherein The secondary ultraviolet curing step is a method for producing a prism film, characterized in that the oxygen atmosphere is adjusted by injecting one kind of gas selected from nitrogen gas, argon gas, helium gas and neon gas in the air atmosphere during the secondary curing.

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